He was only 19

"I watched relationships break up and unemployment set in and all sorts of alienation and dislocation happen," the musician and songwriter told 666 ABC Canberra Mornings presenter Genevieve Jacobs.

It was those memories of the Vietnam War that inspired Schumann to write one of Australia's most iconic songs, "I was only 19".

The song is now dear to the hearts of war veterans Australia-wide, regardless of the conflict they have been involved in.

Schumann said he was born at a time when Vietnam and national service was on his "horizon".

"As it happened the government knocked the head on Vietnam and conscription before my marble went to go in the barrel, but I saw friends of mine who did go to Vietnam come back fundamentally altered," he explained.

Meeting his muse

Schumann said he had wanted to write a song about Vietnam veterans for many years but it was not until a decade had passed that he found an appropriate way of crafting the song, after meeting Vietnam veteran Mick Storen at a gig.

"Had it not been for Mick Storen and his courage, I suppose, in stepping out of what was then the closed circle of Vietnam veterans and telling his story to a songwriter in a left-wing folk rock band from Adelaide, then 19 might not have, well it wouldn't have happened," Schumann said.

Storen later became Schumann's brother-in-law, after his story had been broadcast around the world.

Schumann believes the minute details and the truth in the song were pivotal to its success.

"I think because it is a true story, I think that is important, and I think the detail," he said.